Defrosting refrigerating apparatus



A. L. MATTISON DEFROSTING REFRIGERATING APPARATUS Filed March 28, 1952INVENTOR. "m" "m ARGO I .MATTisoN Aug. 24, 1954 Y l l l l l l l 4lllllllllllllllllllO ATTORNEYS Patented Aug. 24, 1954 UNITED STATESiATENT OFFICE 6 Claims.

This invention relates to a defrosting method and apparatus. In a morespecific aspect it relates to a method and apparatus for defrosting thecooling coil of a low temperature refrigeration system. In a still morespecific aspect, it relates to a method and apparatus for defrosting thecooling coil of a low temperature refrigeration system, using heatavailable in the refrigerant liquefying operation and means.

The cooling coil of low temperature refrigeration systems, 34 F. andbelow, must be defrosted, since frost build up on the coil prevents goodheat transfer, thus lowering the efficiency of the system and making itdiicult or impossible to maintain the desired temperature in therefrigerated space. Defrosting methods and apparatus are known in theart, such methods as using heat furnished by electrical or other meansto melt the frost, in compressor systems sending hot compressedrefrigerant into the coil by operating the compressor during thedefrosting cycle, and simply allowing the refrigerated space to warm upto a point where the frost will melt, and other methods. The methodsknown in the art are not satisfactory, being either expensive to operateor time consuming or both. Many commercial installations have` to bedefrosted several times daily and valuable refrigerated meat,vegetables, etc., have to be protected.

I have invented a new method and apparatus for defrosting the coolingcoils of low temperature refrigeration systems, which defrosts rapidlyand inexpensively. In carrying out the process of my invention, therefrigeration cycle operation is shut down and liquid refrigerant iswithdrawn from the cooling coils when the coils are frosted and it isdesired to defrost. The liquid refrigerant is vaporized and resultingvapors are passed into the cooling coil wherein they give up heat, theheat given up melting the frost. In carrying out one embodiment of myinvention, heat from the refrigerant liquefying method and means, duringrefrigeration cycle operation, is stored up in a heat storage materialand subsequently used to vaporize the liquid refrigerant withdrawn fromthe cooling coils during defrosting cycle operation.

The method and apparatus of my invention has many advantages. My methodis easy and inexpensive to operate and the apparatus is cheaply andeasily installed. The defrosting system of my invention can be builtinto existing refrigeration systems or incorporated in newinstallations. It can be used with compression refrigeration systems,using either a compressor with a positive displacement mechanism or animpeller, and it can be incorporated into absorption refrigerationsystems. The new defrosting method and apparatus of my invention can beused on all types of refrigeration xtures, such as, reach-in fixtures,walk-in fixtures, display cases (either open or closed), locker plants,sharp freezers, etc., and with all types of refrigerant meteringdevices, such as, expansion valve, capillary tube, float valve,restrictor, or any other type of refrigerant control. The coolingsurface in the refrigerated space, usually referred to as the coolingcoil, can be a single coil, a plurality of coils in parallel or series,etc., utilizing in cooling the refrigerated space, forced convection,natural convection, direct contact, a combination of such heat transfermethods, etc. Multiple coiling coils can be defrosted separately orsimultaneously, as desired, using the process and apparatus of myinvention. The defrosting method and apparatus of my invention can beoperated manually, automatically or a combination of manual andautomatic control. It can be operated by a time controller, preferablyeither refrigeration cycle running time or predetermined clock time, apressure controller, preferably acting in response to cooling coilpressure, a temperature controller, preferably acting in response tocooling coil temperature or difference in temperature betweenrefrigerated space temperature and cooling coil temperature, acombination of such controllers, or any other suitable control system.Heat used to vaporize liquid refrigerant from the cooling coil can befrom an external source or it can come from available heat in therefrigeration system. If my defrosting method and means is used on acompressor type refrigeration system, the compressor is not subjected tohigh back pressures or liquid slugging, and use of suction valves,solenoid valves, etc., is not interfered with. Positive return oflubricating oil used in conjunction with the refrigerant is provided forin preferred embodiments of the method and apparatus of my invention.The defrosting method and apparatus of my invention is applicable to avery wide range of refrigeration system capacities, fills a need of longstanding in the art, and is indeed, a great step forward in the art.

It is an object of my invention to provide new defrosting method andapparatus.

It is another object of my invention to provide rapid and economicalmethod and apparatus for defrosting the-cooling coil of a lowtemperature refrigeration system.

Still another object of my invention is to provide rapid and economicalmethod and apparatus for defrosting the cooling coil of a lowtemperature refrigeration system, using heat available in therefrigerant liquefying operation and means.

Other objects and advantages of my invention will become apparent to oneskilled in the art upon reading this disclosure.

In the drawings Fig. l is a schematic ow sheet showing a preferredembodiment of the defrosting process and apparatus of my invention,shown in use with a compressor refrigeration system. Fig. 2 is aschematic flow sheet depicting another preferred embodiment of theprocess and apparatus of my invention, shown' in use with a compressorrefrigeration system. Figs. 1 and 2 are schematic except that in thesystem shown inv Fig. 1 it is preferred that the receivery be disposedbelow the cooling coil (as shown) and the heat exchanger be disposedbelow the receiver 28 (as shown) and, likewise, inthe system shown inFig. 2 it is preferred that the receiver be below the coolingr coil and:theA container be below the receiver 2.8, so that in either case liquidrefrigerant from the coolingcoil will flow by gravity into the receiverand thence intofthe heat exchanger or container as the case maybe.

In the following'discussion ofthe process and apparatusof my` invention,reference is made to Figs..1 and 2,. The same reference numerals areusedfon Figs. l and'2 to `indicate the same equipment. It is to be.understood that the following discussion is not to unduly'limit-thescope of my invention.

Referring now to the drawings, compressor 4, condensing coil 6, receiverfor condensed refrigerantf, line I for transfer of refrigerant tocooling coil I2, refrigerant,- metering device shown as valve I4,cooling coil I2 and suction line I6r comprise ay usual refrigeration;system; The temperature in the; refrigerated space I8 is showncontrolled in ausual manner'by temperature controller 2,0, which startsand stops motor 22 in response to thetemperature in'refrigerated spaceI\8f. The refrigeration system shown in Figs. l and 2 utilizes forcedconvection and, motor 24 turnsthe fan shown'which moves air acrosscoolingcoil I2.

In the embodiment of my defrosting method and-apparatus shown in Figs. 1and 2, the equip.- ment vadded to orl incorporated in the refrigeration`system is-conduit 2 t`with receiver 28 and control valve; 3i)4 therein.Receiver 28 can be dispensed with, if desired, depending on the type ofcooling coil I2 used. If coil I2 is a typewhich operates. withl enoughliquid refrigerant forl the defrosting operation, receiver- 28need notbe used. Heat exchange coil 3,2 to trap liquid refrigerant fromreceiver28, and in which same is vaporized, is added to suction line I6. Inthesystem shown in Fig. 1, motor 34 turns the fan shown, which blows airatroom temperature over coil 32 to vaporize refrigerant therein. As willbe apparent to` thosel skilled inthe art, otherk heating means can beused, such as heat from water, steam, electrical heat, etc. In thesystem shown in Fig. 2, coil 32- is placed inside an insulated container36.v which is filledY witha heat storage material, preferably a materialwith melting point such that it will melt when heatedbycompressed-refrigerant from compressor 4, which passes through coil 33inside container 36, and will solidify giving up heat to vaporizerefrigerant in coil 32. Petroleum Wax, and like materials of low vaporpressure at relatively highV temperature, can be advantageously used.Dowtherm, which has a low vapor pressure at relatively high temperature,can be used, if desired.

In the defrosting method of my invention shown in Fig. 1, operation isas follows: Cooling coil I2 temperature at control point 4u will dropduring the operation of the refrigeration cycle due to frost build-uponthe coil. When coil temperature at point 40 drops to the point at whichtemperature controller 42 is set to operate on the low'side, thecontroller shuts off motor 22, discontinuing the refrigeration cycle,and motor 24, stopping the passage of air over the cooling coil, andopens valve 30 and turns on motor 34, starting the passage of air overcoil 32. Liquid refrigerant which is accumulated in receiver 28 duringoperation of the refrigeration cycle and liquid refrigerant in thecooling coil flows by gravity through conduit 2t, valve 33, conduit I6and into coil 32, wherein it is vaporized. Resulting vapors pass back upline IB into cooling coil I2, wherein'they` are condensed. The heatgiven up is transferred through the walls of the coil and melts frost.Refrigerant condensed in coil I2, then repeats the cycle until all thefrost isymelted... At the end of the defrosting operation, thecoiltemperature at point 4t, which will have risen during defrosting, willhave reached the point at which temperature controller 42 is set tooperate onthe high side. The controller then acts to shut valve 3@ andshut off motor 34, and turns on motor 22. The refrigeration cycle isthen in operation. It is desirable to have controller 42.- or anothercontroller delay the starting-.ofmotor 24, so that the coil I2 is coldbefore air iscirculated across the coil.

Thefsystem shown in Fig. 2 operates substantially in the-same manner asthe system shown inV Fig. 1 andy discussed hereinbefore. During therefrigerationcycle inthe system shown in Fig. 2, hot compressedrefrigerant from compressor 4 is` passed through coil 38 in insulatedcontainer 3.6,and gives-up heat to the heat storage material therein.The heat, stored up is usedto vaporize liquid refrigerant from coil I2and receiver 28, trapped in. coil 32, during the defrosting cycle. Time.controller 44l isset to start defrost cycle by shutting-off motors 24and 22 and opening valve 3.0- preferably according to refrigerationcycle running time or'predetermined clock time, and to close-valve 30and startmotor 22, preferably according to` a set time for defrostoperation. Delayed starting'of motor 24 is desirable as setforthhereinbefore in regard tothe system` shown in. Fig. 1. Bypass line46 in Fig, 2 can be advantageously used to allow the liquid refrigerantto. enter coil 32. from the bottom, if desired.

Lubricating oil normally used in conjunction with refrigerant causes nodifficulty, and any entering coil 32 during defrost operation is pickedup by krefrigerant during refrigeration cycle operation. For this reasonit is desirable that vapors from coil I2 during refrigeration cycle comeinto Contact with a portion of coil 32 where such oil would collectduring the defrosting cycle. If desired, suction line I6 can bypass coil32, and a` separate conduit, tied into line I6 or directly into thecoil, for vaporized refrigerant to cooling coil I2 can be used, with anoil return line from the bottom of coil 32 to compressor 4.

Since coil I2 pressure during refrigeration cycle is effected by frostbuild-up, that is, as frost builds up, coil pressure goes down, themethod and apparatus of my invention can be controlled by` a pressurecontrolleracting in response to coil I2 pressure. And, aswill beapparent to those skilled in the art, other control means can be`frosting operation, and to stop defrosting operation and startrefrigeration cycle after the cooling coil was defrosted. The systemused was the system shown in Fig. 1 with temperature controller 42replaced with the pressure controller.

' It is to be understood that the conditions, etc.,

set forth in the examples are not to unduly limit `the scope of myinvention.

Example I A run was made on a system like that shown in Fig. 1 of thedrawings with a pressure controller used instead of temperaturecontroller 42. Compressor 4 was a positive displacement compressor, andmotor 22 was a 1/3 H. P. electric motor. An electric motor driven fanwas used to circulate air in the refrigerated space over coil I2, and anelectric motor driven fan was used to circulate air at room temperatureover coil 32 during defrosting operation. The refrigerant was Freon 12,and the compressor was shut on and off during refrigeration cycleoperation by a temperature controller, acting in response to thetemperature in the refrigerated space. The pressure controller shut offmotor 24 when defrost operation started, and the starting of motor 24was delayed until coil I2 temperature had dropped to refrigeration cyclenormal after starting refrigeration cycle operation when coil I2 wasdefrosted.

The pressure controller shut off motors 22 and 24, opened valve 30 andstarted motor 34 when coil I2 pressure got down to 2 p. s. i. a. Itclosed valve 30, started motor 22 and shut oi motor 34 when coil I2pressure reached 40` p. s. i. a.

On refrigeration cycle the refrigerated space was held at F.

When coil I2 had no frost, the coil pressure ranged between 4 and 21 p.s. i. a. as refrigeration cycle was on and off. Gradually, as frostbuilt up on coil I2, over a period of 131/2 hours, coil I2 pressuredropped to 2 p. s. i. a. when refrigeration cycle was on. At this timethe pressure controller acted to switch the system to defrostingoperation.

The coil was defrosted in the rapid time of 2G minutes, at `which timecoil I2 pressure had reached 40 p. s. i. a. rThe pressure controllerthen acted to start refrigeration cycle. During defrosting thetemperature in the refrigerated space rose to 13 F. maximum, but in over1/2 the time required from start of defrosting to 0 F. normaltemperature operation, the temperature was not over F. The temperatureof the air passed over coil 32 was 55 F.

Example II Another run was made on the same system with the temperatureof the air passed over coil 32 at 68 F. As in the rst run, defrostoperation was started when coil I2 pressure reached 2 p. s. i. a. andrefrigeration cycle was started when coil I2 pressure reached 40 p. s.i. a.

The coil was defrosted in 14 minutes. During defrosting, the temperaturein the refrigerated space reached a maximum of 11 F., and again thetemperature remained below 5 F., for over 1/2 the time from start ofdefrost to normal refrigeration cycle temperature of 0 F.

As will be evident to those skilled in the art, various modifications ofthis invention can be made, or followed, in the light of this disclosureand discussion, without departing from the spirit or scope of thedisclosure or from the scope of the claims.

I claim:

1. In a refrigeration system, comprising, in combination, cooling coils,blower means to circulate air cooled by said coils, a compressor, a rstconduit for refrigerant connecting the discharge ofsaid compressor withthe inlet of said cooling coils and having compressed refrigerantcooling means, refrigerant metering means adapted to meter refrigerantinto said cooling coils, and a second conduit for refrigerant connectingthe outlet of said cooling coils with the suction of said compressor,that defrosting apparatus which comprises, in combination, a thirdconduit connecting the inlet of said cooling coils and said secondconduit, a receiver in said third conduit adapted to receive liquidrefrigerant from said rst conduit during refrigeration cycle and fromsaid cooling coils by gravity flow, a control valve in said thirdconduit between said receiver and said second conduit, and heating meansin said second conduit between said compressorand the point ofconnection between said second and third conduits adapted to receiveliquid refrigerant from said receiver by gravity flow when said controlvalve is open during defrost cycle and to vaporize liquid refrigerantpassed therein, and said defrosting apparatus being adapted on suchdefrost cycle to pass vaporized refrigerant from said heating meansupwardly through said second conduit, third conduit, control valve andreceiver into the inlet of said cooling coil and upwardly through saidsecond conduit into the outlet of said cooling coil.

2. In a refrigeration system, comprising, in combination, a coolingcoil, means to liquefy refrigerant, a first conduit for return ofvaporized refrigerant from the outlet of said cooling coil to saidrefrigerant liquefying means, a second conduit for refrigerant from saidrefrigerant liquefying means to the inlet of said cooling coil, thatdefrosting apparatus comprising, in combination, a third conduitconnecting the inlet of said cooling coils and said first conduit, avalve in said third conduit, and heating means in said rst conduitbetween said refrigerant liquefying means and point of connectionbetween said .first and third conduits adapted to receive liquidrefrigerant from said cooling coil by gravity flow when said Valve isopen during defrost and to vaporize refrigerant passed therein, and saiddefrosting apparatus being adapted on such defrost to pass vaporizedrefrigerant from said heating means upwardly through said rst conduit,third conduit and valve into the inlet of said cooling coil and upwardlythrough said rst conduit into the outlet of said cooling coil.

3. The apparatusv of claim 2 wherein said third conduit has a receivertherein between said valve and point of connection between said thirdconduit and inlet of said cooling coil, said receiver being adapted toreceive liquid refrigerant from said second conduit during refrigerationcycle operation and from said cooling coil by gravity flow.

4. The apparatus of claim 1 wherein said heating means comprises aninsulated container having a first coil therein to receive liquidrefrigerant from said receiver, and a second coil therein in flowrelationship with said compressor and said compressed refrigerantcooling. meansk adapted to receive compressed refrigerant fromY saidcompressorsaid container being filled with a heat storage material.

5. The apparatus of claim 2 wherein said heating means comprises acontainer filled withY heat storage material, having a rst coil thereinin flow relationship in said rst conduit with said outlet of saidcooling coil and said refrigerant liquefying means adapted-to receiveliquid refrigerant from saidcooling coil and a second coil in saidcontainer, said second coil in said container being a part of saidrefrigerant liquefying means and adapted to transmit heat given upduring refrigerant liquefaction to said heat storage material.

6; In a refrigeration system, comprising, in combination, a cooling coilin a refrigerable space, a compressor, a conduit for refrigerantconnecting the suction of said compressor with the outlet of saidcooling coil, and a conduit for refrigerant connecting the inlet of saidcooling coil with the discharge of said compressor and having compressedrefrigerant cooling means, that apparatus fo-r defrosting said coilwhich comprises, in combination, a receiver in said refrigerable spacehaving an inlet and an outlet and being positioned below said coolingCoil, said receiver inlet connected to said last-named conduit betweensaid refrigerant cooling means and said inlet of said cooling coil, saidreceiver outlet 8 beingconnectedbya conduit with a;valv`e therein tosaid first-named conduit, and said receiver adapted' to receive liquidrefrigerant" from., said cooling coil by gravity flow and to receive andhold liquidl refrigerantv during refrigeration operation with said valveclosed, and a heat exchanger in said first-named. conduit between saidcompressor andpoint of connection of said conduit from said receiver,said heat exchanger beingy positioned below said receiver and beingadapted"` to receive liquid refrigerant from said receiver by gravity owwithsaid valve'open and to vaporize liquid refrigerant passed therein,and said defrosting apparatus being adapted on defrost operation to passvaporized refrigerant from said heat exchanger upwardly through aportion of said. first-named conduit, valve andreceiver into saidcooling coil through its inlet and upwardly through a portion ofsaidfirst-named conduit and into said cooling coil through its'outlet.

References Cited in the iile of thispatent UNITED STATES PATENTS 25Number Name Datev 2,430,960 Soling Nov. 18, 1947 2,452,102 Cocanour Oct.26, 1948 2,524,568 Kritzer Oct. 3, 1950 2,554,848 Warren May 29, 1951

